[Python-3000] set literals

[Nick Coghlan]

Guido van Rossum wrote:
> I've also sometimes thought of unifying dicts and sets by implementing
> set operations on the keys of dicts only. When the values aren't the
> same, we could make an arbitrary decision e.g. the left operand wins.

If the right operand always won then a |= b would be equivalent to a.update(b).

> # And of course it would solve the empty set notation problem nicely:
> assert dict() == {} == set()

So dicts would always start life using the set implementation, and switch to 
the full dict implementation only when a non-None value was added?

> Unfortunately we couldn't redefine <=, <, >=, > to mean various
> subset/superset tests without backwards incompatibilities (but does
> anyone care?

You mean those are defined *now*? I'm trying to figure out what the heck they 
could even mean. . .

> I still expect there's a fatal flaw in the scheme, but I can't think
> of it right now...

If you've got an idea of how to handle the promotion from the set 
implementation to the dict implementation when a non-None value is entered, 
then I can't see any fatal flaws, either.

I'm sure Raymond will be able to come up with something, though :)

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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